The invention relates to a spool type fluid control valve, either hydraulic or pneumatic, which operates under high pressure.
Spool valves which operate under high pressure generally are manufactured with metal-to-metal contact between the bore and the internal valve spool lands. When used in high pressure applications, leakage occurs between the bore and lands even though considerable expense is incurred in polishing the surfaces of the bore and valve lands to an extremely small tolerance. Therefore, it is common practice to include elastomer type seals between the bore and outermost lands of the spool to prevent external leakage of the fluid. In high pressure applications, the use of elastomer type seals between the bore and the outermost spool lands is not entirely satisfactory because such seals bind and the high friction forces make it difficult to shift the spool. Moreover, such seals deform under high pressure and are forced into surface imperfections in the bore resulting in abrasion of the elastomer seal as the spool is shifted.
There is therefore a need for a high-pressure spool-type fluid control valve which can utilize elastomer type seals which do not bind due to high friction and which have increased life and minimal failure compared to present valve designs.